The NHRC-Squelch is a microprocessor-controlled carrier-activated
switch on a single circuit board. It is intended for use in
repeater systems, to provide a source of the CAS signal independent
of the radio's squelch circuitry.

The NHRC-Squelch requires discriminator audio as its only input,
and continuously evaluates the amount of noise that is present.
Extremely quiet signals are subject to instant squelch action,
noisier signals increase the amount of hysteresis in the squelch action,
resulting in progressivly longer delays as signal quality degrades.
This allows the repeater to properly "follow" weak mobiles
as they fade from "mobile flutter."